format binary
use32
org 0x100000

MULTIBOOT_HEADER_MAGIC      equ 0x1BADB002
MULTIBOOT_PAGE_ALIGN        equ (1 shl 0)
MULTIBOOT_MEMORY_INFO       equ (1 shl 1)
MULTIBOOT_VIDEO_REQUEST     equ (0 shl 2)
MULTIBOOT_AOUT_KLUDGE       equ (1 shl 16)
MULTIBOOT_HEADER_FLAGS      equ MULTIBOOT_PAGE_ALIGN or MULTIBOOT_MEMORY_INFO or MULTIBOOT_VIDEO_REQUEST
MULTIBOOT_HEADER_FLAGS      equ MULTIBOOT_PAGE_ALIGN or MULTIBOOT_MEMORY_INFO or MULTIBOOT_VIDEO_REQUEST or MULTIBOOT_AOUT_KLUDGE
MULTIBOOT_CHECKSUM          equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)

multiboot:
	dd MULTIBOOT_HEADER_MAGIC
	dd MULTIBOOT_HEADER_FLAGS
	dd MULTIBOOT_CHECKSUM
	dd multiboot	; header address
	dd 0x100000	; load address
	dd stack_bottom	; load end address
	dd stack_top	; bss end address
	dd start	; entry address
	dd 0	; video mode_type (0:fb, 1:txt) (set flags[2]!)
	dd 1024	; video width
	dd 768	; video height
	dd 32	; video depth

start:
	; Setup stack
	mov ebp, stack_bottom
	mov esp, stack_top

	push ebx
	push eax

	cmp eax, 0x2badb002
	jne multibootnomagic

	mov byte [0xb8000], '!'

	push stuff.bootmsg
	call printbootmsg
	call serialinit
	call serialwrite
	add esp, 4

	jmp hang

hang:
	cli
	hlt
	jmp hang

multibootnomagic:
	mov esi, .msg
	mov edi, 0xb8000
	mov ah, 64
	cld
.loop:
	lodsb
	or al, al
	jz .done
	stosw
	jmp .loop
.done:
	jmp hang
.msg db "No multiboot magic", 0

printbootmsg:
	push ebp
	mov ebp, esp
	pushad
	mov esi, [ebp+8]
	mov edi, 0xb8000
	cld
.loop:
	lodsb
	or al, al
	jz .done
	stosb
	inc edi
	jmp .loop
.done:
	popad
	pop ebp
	ret

include "src/serial.asm"

stuff:
	.bootmsg db "=== KoalemOS ===", 10, 0


stack_bottom:
rb 16384
stack_top: